Well for me I can SAVE at the point the Quest stoppage happens and then load that save and it is fine. What ever stopped the script seems that it is some a temporary issue or at least one that is not save in the savegame.
So that could mean it is related to a SKSE function. NOW I am not saying it is the FAULT of SKSE only that most SKSE functions are NOT saved in the save game so it may be a "bad" use of one of those commands.
Or there is some other part of the game that stops quest for some reason.
I know... that is not much to go on.
99% of my users do not have the issue. Only me and one other guy (user of my mod) that I know of.
I believe I'm having the same problem. For some people they will not start after reloading a game. For others they crash during use. I only use my quest to handle scripts. These script crashes include the one to run MCM. Several have reported that after re-loading a save the option for my mod is gone and nothing is responding. I tried a SEQ file with no luck.